fix: patch plan mode (#211)

Co-authored-by: Letta <noreply@letta.com>

src/tools/impl/ExitPlanMode.ts

@@ -6,6 +6,7 @@
 export async function exit_plan_mode(): Promise<{ message: string }> {
   // Return confirmation message that plan was approved
   // Note: The plan is read from the plan file by the UI before this return is shown
+  // The UI layer checks if the plan file exists and auto-rejects if not
   return {
     message:
       "User has approved your plan. You can now start coding.\nStart with updating your todo list if applicable",